A workman smooths out the gravel near the base of British artist Alex Chinneck' latest sculpture “A bullet from a shooting star” on the Greenwich Peninsula in London on September 17, 2015. The 35-metre tall, upside-down electricity pylon overlooks the Canary Wharf financial district. (Photo by Leon Neal/AFP Photo)

A masked man in military fatigues brings a blindfolded Irma Krat, arrested and held by pro-Russian protestors before her meeting with journalists near of occupied police station in Slaviansk, Ukraine, 21 April 2014. Pro-Russian activists are demanding broader autonomy from Kiev and closer ties to Russia. Pro-Russian activists continued occupying government, police and other administrative buildings in eastern Ukrainian cities, in defiance of an ultimatum by the Ukrainian government to lay down their weapons. Russia, the United States, the European Union and Ukraine on 17 April had agreed on steps to de-escalate the crisis in Ukraine during talks in Geneva, Switzerland. (Photo by Roman Pilipey/EPA)

Star Wars actors on the Cantina set at Star Wars Celebration: The Ultimate Fan Experience held at the Anaheim Convention Center on Thursday, April 16, 2015, in Anaheim, Calif. (Photo by Richard Shotwell/Invision/AP Photo)

A South Sudanese model applies make-up during the Festival of Fashion and Arts for Peace in Juba August 9, 2014. (Photo by Andreea Campeanu/Reuters)

NASA's DHC-3 Otter plane flies in Operation IceBridge-Alaska surveys of mountain glaciers in Alaska in this image released on September 18, 2014. Over the past few decades, average global temperatures have been on the rise, and this warming is happening two to three times faster in the Arctic. (Photo by Chris Larsen/Reuters/NASA/University of Alaska-Fairbanks)

Two Bulgarian tourists pose in front of the Eiffel Tower in Paris on their last day in the capital on March 24, 2014. (Photo by Franck Fife/AFP Photo)

The sculpture “It Takes Two to Tango” by Scottish sculptor David Mach is seen in front of the headquarters of the CMA-CGM shipping company office tower in the port of Marseille, France, March 15, 2016. (Photo by Jean-Paul Pelissier/Reuters)

Joshua Patino stands on a ladder to put finishing touches on a giant dinosaur exhibit at PAX East in the Boston Convention and Expo Center, Thursday, April 21, 2016, in Boston. PAX East, an annual celebration of gaming culture, is expected to draw tens of thousands of visitors Friday through Sunday. It's a place where serious gamers can preview unreleased video games and devices, compete in tournaments, hear live music and meet others for whom gaming is a way of life. (Photo by Elise Amendola/AP Photo)